This invention relates to the raising and lowering of ventilation curtains on poultry houses and the like, and more particularly to the combination of power driven means and manual means for raising and lowering such curtains, the manual means being utilized in the event of a power failure for incrementally raising and lowering the curtains.
A poultry house wherein chickens or the like are confined while they are raised for market must be maintained under reasonably controlled temperature and ventilation conditions. Such poultry houses have screened windows in the sidewalls with a weather impervious curtain movably disposed for covering each window to close off ventilation and prevent the houses from becoming too cold, and for opening the windows when the temperature within the house becomes too warm. Conventionally, the curtains are raised and lowered to close and open the windows and this may occur in increments dependent upon the temperature within the chicken houses and the ventilation required to provide necessary fresh air for the health of the poultry.
In the early prior art the curtains were raised and lowered manually by means of winches and pulleys, examples of such devices being illustrated in Wyman U.S. Pat. No. 1,054,071 and Haggard U.S. Pat. No. 3,478,805. Because of the frequency of the required raising and lowering of the curtains, automatic electric power operated means have been provided. Examples of such power operated means in the prior art are illustrated in Dubie et al. U.S. Pat. No. 3,042,001 and Thomason U.S. Pat. No(s). 3,429,298 and 3,474,761. Additionally, ventilation fans are provided for ensuring adequate air flow through the houses. However, should a power failure or the like occur with the curtains in the closed position, the temperature and ventilation within the poultry house can rapidly reach conditions resulting in injury or death to the poultry. Thus, the prior art has proposed safety devices for automatically releasing a normally operable winch which has been used to move the curtains to the closed position. For example, in Smith U.S. Pat. No. 3,973,173 and in Sutton, Jr. U.S. Pat. No(s). 3,915,377 and 4,428,278 a safety device is actuated upon failure of the electrical system to release a winch and allow it to free-wheel to permit the curtains to drop and open the windows to the poultry house. In no known prior art is a combination power driven means and manually operable means utilized for controlling the raising and lowering of the curtains such that normally the curtains are raised and lowered automatically by power driven means, but in the event of a power failure, the curtains may be raised and lowered incrementally manually.